Little by little, literally “a little a little,” may mean “by and by” (Holladay), but here the idea seems to be “gradually” (Translator’s Old Testament). I will drive them out from before you is identical with verse 29. Until you are increased is literally “until when you [singular] are fruitful,” or “until you reproduce and increase in number.” The same word is translated “multiply” in 1.10 and 12. And possess the land means to “occupy the land as your possession” (Durham). Good News Translation makes it clear: “until there are enough of you to take possession of the land.”

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .